Sugar cookies, clear doctor visits, no burglars allowed, and best of all... a new kitty in the house! I liked my daughter naming her calico cat Cali, I thought it was cute. That's my suggestion to add to the list of possibilities. Start putting something soft with the other cat's scent in where she is, and something from her where they are. It will help them adjust to the scent. Then supervise a few minutes of one-on-one time each day. Before long they will be safely together and in a month or two they will be getting along just fine. There is always this jostling to adjust to newcomers, most often the older ones will eventually adopt the new kitten as one of their own. :-)

Thanks, Josie! We're currently keeping her in the family room, with a little litter box in the bathroom. The boys have the rest of the house. The older one (10 yrs) has stopped hissing when he sees her. He mostly looks bewildered - not sure what she is! The younger one (8 yrs) is NOT happy. He's hissing and growling (he's the Alpha cat as it is). Hopefully, he will calm down in a few days. Thank you so much for your suggestions!